An encoder is a device or method for transforming a form or format of information for standardization, secrecy, increase of processing speed, memory space saving, and so on. A quantization parameter is a numerical value for adjusting the degree of quantization in an encoder. An encoder may quantize input data using a quantization parameter.
Conventional encoders determine an optimal encoding quantization parameter using rate-distortion optimization (RDO) within a range of quantization parameters by comparing the cost of all possible candidates. However, an encoder that performs RDO may use a significant amount of computation to determine an optimal encoding quantization parameter without certainity that the quantization parameter determined by the encoder is the optimal one.